[PATCH 6.6.y 2/2] PCI: endpoint: Avoid creating sub-groups asynchronously

[Sasha Levin <sashal@kernel.org>]

From: Liu Song <liu.song13@zte.com.cn>

[ Upstream commit 7c5c7d06bd1f86d2c3ebe62be903a4ba42db4d2c ]

The asynchronous creation of sub-groups by a delayed work could lead to a
NULL pointer dereference when the driver directory is removed before the
work completes.

The crash can be easily reproduced with the following commands:

  # cd /sys/kernel/config/pci_ep/functions/pci_epf_test
  # for i in {1..20}; do mkdir test && rmdir test; done

  BUG: kernel NULL pointer dereference, address: 0000000000000088
  ...
  Call Trace:
   configfs_register_group+0x3d/0x190
   pci_epf_cfs_work+0x41/0x110
   process_one_work+0x18f/0x350
   worker_thread+0x25a/0x3a0

Fix this issue by using configfs_add_default_group() API which does not
have the deadlock problem as configfs_register_group() and does not require
the delayed work handler.

Fixes: e85a2d783762 ("PCI: endpoint: Add support in configfs to associate two EPCs with EPF")
Signed-off-by: Liu Song <liu.song13@zte.com.cn>
[mani: slightly reworded the description and added stable list]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@kernel.org
Link: https://patch.msgid.link/20250710143845409gLM6JdlwPhlHG9iX3F6jK@zte.com.cn
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/pci/endpoint/pci-ep-cfs.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/pci/endpoint/pci-ep-cfs.c b/drivers/pci/endpoint/pci-ep-cfs.c
index a2b81a64fcd11..c28c3f094496a 100644
--- a/drivers/pci/endpoint/pci-ep-cfs.c
+++ b/drivers/pci/endpoint/pci-ep-cfs.c
@@ -23,7 +23,6 @@ struct pci_epf_group {
 	struct config_group group;
 	struct config_group primary_epc_group;
 	struct config_group secondary_epc_group;
-	struct delayed_work cfs_work;
 	struct pci_epf *epf;
 	int index;
 };
@@ -100,7 +99,7 @@ static struct config_group
 	secondary_epc_group = &epf_group->secondary_epc_group;
 	config_group_init_type_name(secondary_epc_group, "secondary",
 				    &pci_secondary_epc_type);
-	configfs_register_group(&epf_group->group, secondary_epc_group);
+	configfs_add_default_group(secondary_epc_group, &epf_group->group);
 
 	return secondary_epc_group;
 }
@@ -160,7 +159,7 @@ static struct config_group
 
 	config_group_init_type_name(primary_epc_group, "primary",
 				    &pci_primary_epc_type);
-	configfs_register_group(&epf_group->group, primary_epc_group);
+	configfs_add_default_group(primary_epc_group, &epf_group->group);
 
 	return primary_epc_group;
 }
@@ -561,15 +560,13 @@ static void pci_ep_cfs_add_type_group(struct pci_epf_group *epf_group)
 		return;
 	}
 
-	configfs_register_group(&epf_group->group, group);
+	configfs_add_default_group(group, &epf_group->group);
 }
 
-static void pci_epf_cfs_work(struct work_struct *work)
+static void pci_epf_cfs_add_sub_groups(struct pci_epf_group *epf_group)
 {
-	struct pci_epf_group *epf_group;
 	struct config_group *group;
 
-	epf_group = container_of(work, struct pci_epf_group, cfs_work.work);
 	group = pci_ep_cfs_add_primary_group(epf_group);
 	if (IS_ERR(group)) {
 		pr_err("failed to create 'primary' EPC interface\n");
@@ -628,9 +625,7 @@ static struct config_group *pci_epf_make(struct config_group *group,
 
 	kfree(epf_name);
 
-	INIT_DELAYED_WORK(&epf_group->cfs_work, pci_epf_cfs_work);
-	queue_delayed_work(system_wq, &epf_group->cfs_work,
-			   msecs_to_jiffies(1));
+	pci_epf_cfs_add_sub_groups(epf_group);
 
 	return &epf_group->group;
 
-- 
2.51.0